1. Field of the Invention
The present invention relates to a method of preparing silicon nitride from silica.
2. Description of the Prior Art
Silicon nitride powder has been made by the following methods:
1. The reaction of nitrogen and silicon; PA0 2. The vapor phase reaction of silicon tetrachloride or silane with ammonia; and PA0 3. The nitridization of silica with carbon powder.
Each of these methods has deficiences. Method (1) requires silicon metal which is expensive and consequently, the silicon nitride produced is also expensive. Method (2) cannot be used for the mass production of inorganic refractory raw material, while Method (3) requires a long reaction time at elevated temperatures.